Demountable variable length antenna



CROSS REFERENCE SEARCH ROOM m gm Aug. 23, 1966 c. G. COLONY DEMOUN'IABLEVARIABLE LENGTH ANTENNA Filed Dec. 12. 1962 2 Sheets-Sheet 1 FIG. 1

CONTROL SIGNAL INVENTOR. CHARLES G. COLONY ATTORNE Y3 United StatesPatent 3,268 898 DEMOUNTABLE VARIAliLE LENGTH ANTENNA Charles G. Colony,Cincinnati, Qhio, assignor to Avco Corporation, Cincinnati, Ohio, acorporation of Delaware Filed Dec. 12, 1962. Ser. No. 244,039 '6 Claims.(Cl. 343723) The present invention relates to demountable variablelength antennas and more particularly to a variable length antennasupported within a dieelectric mast formed of telescoping mast sections.

In a portable communication station the antenna is an important element.At the same time it is an element which presents inherent difficultieswhich, if not overcome, may counteract to a substantial extent theadvantages possible in the use of miniaturization techniques in radiotransmitters and receivers.

The prime requisite of an antenna is that it be an efficient radiator.Throughout this description and in the claims it will be understood thatthe antenna of the present invention is susceptible for use either as atransmitting or receiving antenna. An antenna which is a good radiatoris inherently a good receiver as well, according to the well-knownprinciple of reciprocity in the design of transmitting and receivingantennas. It is generally a requirement for efiicient radiation that theantenna be of substantial dimension. At the same time, it is re quiredto be easily transported and erected, stable in service and quicklydemountable for removal to another location. In military applications itshould be as inconspicuous as possible.

In many antenna applications, and particularly in military applications,it is desirable that the antenna be suitable over a substantial range offrequencies with a minimum of time loss for antenna tuning, Ideally, anyantenna tuning required should be carried out automatically inconjunction with the tuning of the transmitter or receiver.

In addition to providing the above described features and advantages, itis an object of the present invention to provide an antenna which iseasily erectable or demountable and which includes the capability ofvery rapid antenna tuning by changing the effective length of theantenna radiator. It is another object of the invention to provide anantenna of the foregoing type in which the antenna mast is very compactwhen demounted by virtue of its telescopic construction.

It is still another object of the present invention to provide anantenna of the foregoing type wherein the radiator may be effectivelylengthened or shortened in response to an electrical control signalsupplied to a servomotor.

Other objects and advantages will be apparent from a consideration ofthe following description in conjunction with the appended drawings inwhich:

FIGURE 1 is an elevational view of an antenna according to the presentinvention;

FIGURE 2 is a fragmentary sectional view taken along the line 22 inFIGURE 1;

FIGURE 3 is a fragmentary sectional view of the top portion of theantenna structure illustrated in FIGURE 1;

FIGURE 4 is a sectional view taken along the line 4-4 in FIGURE 3;

FIGURE 5 is a partially sectional view taken along the line 55 in FIGURE1;

FIGURE 6 is a sectional view taken along the line 3,2683% PatentedAugust 23, 1966 graduated size supported end-to-end to form a maststructure.

A lowermost mast section 16 is rigidly secured to a base structure 13which supports the antenna and houses reels for storing the flexibleradiator element and support cord as will later be described.

A housing 14 at the top of the antenna mast contains a pulley and reelmechanism later to be described. The mast may be supported by guy ropes15 if necessary or, in View of its light weight, may in some cases besupported by stakes securing the base 13 to the ground.

In addition to the antenna contained internally within the mast ofantenna assembly 11, the assembly may be utilized to support additionalindependent antennas such as the corner reflector antenna 20 illustratedin dotted lines in FIGURE 1.

As will later be seen the antenna assembly 11 may be demounted bytelescoping or nesting the mast sections 12 into the lowermost mastsection 16. In this case the housing 14 occupies the position shown indotted lines in FIGURE 1, and the antenna assembly is reduced to arelatively small dimension and is easily transportable. The variouselements in FIGURE I particularly the base 13 and the housing 14 shouldnot be considered to be drawn to scale as they may be considerablysmaller relative to the antenna assembly 11. The size of the elements inFIGURE 1 and in the other figures is generally selected for clarity ofillustration rather than as representative of optimum size in apractical device.

As has previously been explained, it is a feature of the presentinvention to provide an antenna which is not only readily demountableand transportable but also is rapidly tunable. The manner in which theantenna is tuned by changing the eifective length of the radiatingelement may be understood by reference to FIGURES 2, 3 and 4.

Referring to FIGURE 2, a conductive radiator element comprising a tape17 is supported within the antenna assembly by a support cord 18 ofdielectric material which may conveniently be a rope or cord of cotton,hemp, or of synthetic fiber such as nylon or the like. As viewed inFIGURE 3, the antenna element 17 and the cord or lanyard 18 comprise atwo-sided continuum.

A pulley or hanger element 51 is provided at the top of the antennaassembly so that the tape 17 may be raised and lowered by means of cord18 as will later be de scribed in more detail.

The tape 17 is conductive and may comprise a thin flexible metal tape.Alternatively, tape 17 may be formed of plastic sheet material such aspolyethylene or polypropylene upon which is coated a film of conductivematerial such as aluminum, silver, or the like.

The unextended portion of tape 17 is stored on a reel 19. Suitable meansis provided for making an electrical connection to the tape 17. In theparticular embodiment illustrated, tape 17 is a metal tape makingelectrical contact to metal reel 19 and thence through a sliding contact21 to the center conductor 23 of 'a coaxial cable 22 or otherappropriate transmission line. The cable 22 would of course be connectedto the transmitter and/ or the receiver associated with antenna assembly11. The outer conductor of cable 22 may be grounded by a suitableelectrical ground connection 24.

The tape 17 may alternatively be electrically isolated from groundpotential by a radio frequency choke. The last few turns of thetape onreel 19 will provide such a choke if the turns are mutually insulated asin the case where the tape comprises a non-conductive base having aconductive film deposited thereon. With such a choke arrangement contact21 should brush on tape 17 directly.

Reel 19 is supported on and keyed to a shaft 25 but is insulatedtherefrom in order to prevent electrical ground- 3 ing of reel 19. Shaft25 is supported within base 13 by supports such as 26.

Shaft 25 and hence reel 19 are driven by an electrical servomotor 29connected to shaft 25 through a suitable flexible coupling 28.

A reel 31 is provided for support cord 18 and is mounted on shaft 25 butis not keyed to the shaft. Reel 31 is coupled to shaft 25 by aclock-spring 32. Spring 32 provides a bias torque which maintainstension in cord 18 and tape 17. Cord 18 and tape 17 are woundrespectively on reels 31 and 19 in opposite senses so that upon rotationof the reels by servomotor 29, tape 17 is paid out while cord 18 isreeled in or vice versa. Any small difference in the rate of pay outbetween the two reels is accommodated by spring 32. In addition to, orin place of, the resilience provided by spring 32 the cord 18 may beresiliently stretchable. Preferably the tape 17 is not stretchable asthe length of the antenna is measured and cantrolled by the pay out oftape 17.

Tape 17 is provided with holes 33 extending longitudinally of the tapewhich provide index marks for measuring the amount of extension of thetape. Obviously the tape could be provided with other index marks suchas notches in the edge, corrugations or the like or imprinted indexmarks could be utilized in connection with a photoelectric sensingmeans.

The sprocket 34 engages the holes 33 and tape 17 and is connected by ashaft 35 to a multiple turn potentiometer and indicator 36. The multipleturn potentiometer 36 may be of conventional design and provides afeedback voltage to servomotor 29 proportional to the length ofextension of tape 17. The potentiometer 36 may be of the indicating typeand a window 37 may be provided for direct reading of the length ofantenna extension. The length of antenna extension is substantiallyproportional to the tuning of the antenna in wavelengths so that thepotentiometer 36 and other controls for the antenna tuning may hecalibrated directly in terms of wavelength (or of frequency which is aninverse function of Wavelength).

The electrical feedback signal from potentiometer 36 is transmitted overleads 38 to servomotor 29 which is also provided with a control signalover leads 39. As is Well known, the function of a servomotor such as 29is to operate to equalize the feedback signal provided over loads 38with the control signal provided over leads 39. This is done by causingextension or retraction of tape 17, and thus the amount of extension oftape 17 is rendered directly responsive to the amplitude (or otherparameter) of the control signal 39.

The servo control for the tuning of antenna assembly 11 is of coursemerely exemplary and any of many known forms of servo control may besubstituted for that schematically illustrated and described forpurposes of explanation.

Referring now to FIGURE 3, the reel housing 14 is supported at the topof the topmost 'mast section 12. Rings 41 may be provided on housing 14to secure guy ropes such as 15 illustrated in FIGURE 1. A storage reelor spool 42 is rotatably mounted within housing 14 on a shaft 43 and iskeyed for rotation therewith.

Shaft 43 is connected through a gear train comprising gears 44, 45, 46and 47 to a clock spring 48 so that reel 42 is pro-loaded to cause tape17 and cord 18 to be wound onto reel 42 as the antenna assembly 11 iscollapsed by telescoping the mast sections 12 into one another and intothe bottom mast section 16. The gear train 44, 45, 46 and 47 causes oneturn of winding or unwinding of spring 48 to result in numerous turns ofreel 42. The outer end of spring 48 is secured to housing 14 by pin 49.As will be seen from FIGURE 3 in conjunction with FIGURE 4, a pulley 51is mounted on reel 42 for free rotation about shaft 52. When the antennais arranged for operation as illustrated in FIGURE 1, the position ofpulley 51 is as shown in FIGURES 3 and 4 allowing tape 17 readily to beraised by cord 18. When the antenna is demounted by telescoping mastsections 12, tape 17 and/ or cord 18 are reeled onto reel 42 by theaction of spring 48. As shown in FIGURES 3 and 4, the spool 42 is formedwith end flanges and an axially extending curvilinear cutout portioninto which the pulley 51 partially extends (FIGURE 4).

Reels 19 and 31, for storage of tapes 17 and 18 dur ing operation of theantenna, and reel 42, for demounted storage of cord 18 and tape 17, are,of course, merely illustrative storage and reeling means for tape 17 andcord 18 and various other arrangements to perform the same function maybe devised by those skilled in the art. By way of example, reels 19 and31 need not be mounted coaxially but may be mounted on parallel axes andcoupled for simultaneous rotation by gearing or other suitable means.

Thus far, the antenna assembly has been explained primarily withreference to its operative or extended position. FIGURES 5, 6 and 7illustrate the construction of mast sections 12 which allows the antennaassembly to be readily telescoped for demounting and at the same timeprovide a strong and light mast structure for supporting the internalantenna radiator and such external antenna structures as the cornerantenna illustrated in FIGURE 1.

Referring now to FIGURES 5, 6 and 7, intermediate mast sections 12 areshown which are of generally similar construction but of graduated sizeso that they fit one within the other. In the preferred form of theinvention illustrated, each individual mast section is also taperedslightly so that it has a somewhat smaller dimension at the top than atthe bottom.

In FIGURE 5 the topmost mast section 12 has a tubular body 60 with anenlarged bottom portion 61. At the bottom of the tube 60 are oppositelydisposed lugs 62 and 63, the latter being shown in dashed lines in FIG-URE 5.

The middle mast section 12 in FIGURE 5 is formed of a tubular body 64and is of similar construction to the upper mast section with anenlarged bottom portion 65 and lugs at the bottom end, only one ofwhich, 66 is shown in dash line. The tubular body 64 is of largerdiameter than the tubular body 60 so that the latter telescopes into theformer.

At the top of tubular body 64 is a collet 67 which prevents over-travelof tubular body 60 with respect to tubular body 64 when the former isbeing extended and which also causes tubular body 60 to fit snuglywithin tubular body 64 to provide a substantially rigid upright mast.

Within tubular body 64 there are two guide members 68 and 69. Guidemember 68 extends substantially to the lower end of tubular body 64 andengages lugs 62 and 63 on tubular body 60 to .prevent undesiredrotational movement between tubular body 60 and tubular body 64.

Guide 69 is shown only in dotted lines in FIGURE 5 and does not extendto the lower end of tubular body 64 as only one guide is needed torestrain rotational movement between successive mast sections.

Guide members 68 and 69 are provided respectively with upwardlyextending stops 71 and 70 which allow relative movement of somewhat lessthan degrees between tubular body '60 and tubular body 64 when theformer has been fully extended. After such rotation tubular body 60 issupported in extended position by the fact that lugs 62 and 63 restrespectively on guide members 68 and 69.

The lower edge 62a of lug 62 and the upper edge 68a of guide member 68are sloped toward stop 71 so that the weight of the mast sections tendsto maintain them in the locked position so that they do notinadvertently become unlocked in the presence of vibration or shock dueto Wind or the like. Of course, guide member 69 and lug 63 havesimilarly sloped edges. If necessary or desired the slope could be madegreater than that illustrated in FIGURE 5 or could be replaced by a stepto provide positive locking.

As previously noted the various mast sections have similar constructionand it may be noted for example that the lower end of guide member 72for hollow tubular body 60 is seen in the sectional View of FIGURE 6.

Wide latitude is possible in selection of materials for construction ofmast sections 12. A light dielectric material is preferable, for examplefiber glass roving laminated with polyester resin. The tube sections maybe further overwrapped with a spiral wrap of laminated fiber glassroving and epoxy resin. Strength and durability will be enhanced if atleast 60 percent of the laminate by volume consists of fiber glassroving.

The lug and guide members forming a part of the mast sections may alsobe formed of laminated fiber glass and may be secured in place by anepoxy resin adhesive.

Virtually any dielectric material of suitable physical strength may beutilized to form the mast sections and they may .be formed by laminatingon a mandrel or they may alternatively be formed of a plastic materialsuch as polyethylene .or polypropylene and cast or molded in a singleunitary piece.

From the foregoing explanation it will be appreciated that an antenna isprovided which occupies a relatively small volume for storage andtransportation and which is readily erected to form an antenna ofsubstantial height eg from 30 to 50 feet high. The mast structure heightis generally fixed and constant in operation, but the internal radiatingelement is of adjustable length to provide a wide range of antennatuning. The adjustment of the radiator length may be accomplished by aservomotor synchronized with the receiver or transmitter tuningadjustment.

Although the antenna particularly described is a monopole antenna, theinvention may be adapted to dipole antennas by utilizing the techniquesdescribed in copending application Serial No. 244,184, tiled December12, 1962 for Extendible Dipole Antenna in the names of John A. Kueckenand Charles Gordon Colony.

In addition to the various modifications of the embodiment of theinvention herein described or suggested, numerous other variations andmodifications may be devised by those skilled in the art. Accordingly itis desired that the scope of the invention not be limited to thoseparticu lar embodiments and modifications shown or suggested but thatthe scope of the invention be determined by reference to the appendedclaims.

1 claims 1. A demountable antenna with radiator of adjustable eflectivelength comprising a plurality of elongated hollow tapered dielectricmast sections arranged to form a telescoping dielectric mast, means forlocking said mast sections in an extended position, means for supportingsaid mast sections in an extended upright position, a freely rotatablepulley positioned in the top of the topmost mast section, a conductiveflexible tape having indexing apertures, a nonconductive elongatedflexible support within said mast sections extending over said pulleyand secured to said tape, respective storage reels for said supportmeans and for said tape positioned at the bottom of said rnast sections,said reels being coupled together to pay out one of said tape andsupport means while the other of said tape and support means is beingtaken in, means for biasing said reels with respect to one another tomaintain tension in said tape and support means, sensing means engagingthe indexing apertures of said tape for generating an electric signal inresponse to the displacement of said tape, a servo-motor electricallyconnected to be responsive to said sensing means and mechanicallyconnected to drive said reels to cause the displacement of said tape tosubstantially correspond to an independent 6 control signal supplied tosaid servomotor, and means for reeling in said tape and said flexiblesupport in conjunction with telescoping of said mast sections.

2. A demountable antenna with radiator of adjustable effective lengthcomprising a plurality of elongated hollow tapered dielectric mastsections arranged to form a telescoping dielectric ma-st, means forlooking said mast sections in an extended position, means for supportingsaid mast sections in an extended upright position, a freely rotatablepulley positioned in the top of the topmost mast section, a conductiveflexible tape having indexing apertures, a nonconductive elongatedflexible support Within said mast sections extending over said pulleyand secured to said tape, respective storage reels for said supportmeans and for said tape positioned at the bottom of said m'ast sections,said reels being coupled together to pay out one of said tape andsupport means while the other of said tape and support means is beingtaken in, means for biasing said reels with respect to one another tomaintain tension in said tape and support means, sensing means engagingthe indexing apertures of said tape for generating an electric signal inresponse to the displacement of said tape, and a servo-motorelectrically connected to be responsive to said sensing means andmechanically connected to drive said reels to cause the displacement ofsaid tape to substantially correspond to an independent control signalsupp-lied to said servo-motor.

3. A demountable antenna with radiator of adjustable effective lengthcomprising a plurality of elongated hollow tapered dielectric mastsections arranged to form a telescoping dielectric mast, means forlocking said mast sections in an extended position, means for supportingsaid mast sections in an extended upright position, .a freely rotatablepulley positioned at the top of the topmost mast section, a conductiveflexible tape having indexing apertures, a nonconductive elongatedflexible support extending over said pulley and secured to said tape,respective storage reels for said support means and for said tapepositioned at the bottom of said mast sections, said reels being coupledtogether to pay out one of said tape and support means while the otherof said tape and support means is being taken in, means for biasing saidreels with respect to one another to maintain tension in said tape andsupport means, and sensing means engaging the indexing apertures of saidtape for sensing the displacement of said tape.

4. An antenna with radiator of adjustable effective length comprising aplurality of elongated hollow dielectric mast sections adapted to nestone within another in a demou-nted position and to engage end-to-end inan operative position, means for supporting said mast sections in anupright position engaged end to end, and a radiator element ofadjustable effective length supportable in an upright position by saidend-to-end engaged mast sections, said element comprising an elongatedflexible conductive element, elongated flexible nonconductive supportmeans secured to said conductive element for controllably positioningsaid conductive element longitudinally of said end-to-end engaged rnastsections means including an idler pulley for drawing in and forextending said support means and means including a spool on which theidler pulley is mounted for storing the unextended portions of saidsupport means and said conductive element.

5. A collapsible antenna comprising:

a plurality of hollow dielectric telescoping mast sections including atop section and a bottom section and adapted to be extended as anelongated antenna support or to be nested;

first and second storage reels positioned at the bottom of said rnastsections;

a spool mounted for rotation at the top of the top mas-t section, saidspool being formed with end flanges and an axially extending curvilinearcutout portion;

an idler pulley rotatably mounted on said flange and disposed at leastin part within said cutout portion;

a flexible antenna and a flexible halyard joined to form a continuumlooped around said pulley, the antenna being reeled or unreeled by theother of said storage reels;

and spring means for biasing said spool so that, as the dielectric mastis collapsed, the spool is turned and the axis of the pulley rotatesabout the axis of the spool, whereby the continuum is Wound up.

6. A collapsible antenna comprising:

a plurality of hollow dielectric telescoping mast sections including atop section and a bottom section and adapted to be extended as anelongated antenna support or to be nested;

a hanger element mounted at the top of the top mast section;

a flexible antenna and a flexible halyard joined to form a two-sidedcontinuum looped around said hanger element;

means for reeling in and out said antenna and halyard;

and spring-urged means for simultaneously reeling in both sides of saidcontinuum in the same direction as the mast sections are nested.

References Cited by the Examiner UNITED STATES PATENTS 2,119,692 6/1938Voigt 343-723 X 2,283,524 5/1942 White 343-723 X 2,366,634 1/1945 Ludwig343-883 2,424,598 7/1947 Willough'by 343-723 2,522,222 9/1950 Haller343-723 X 2,834,012 5/1958 Allen 343-723 FOREIGN PATENTS 903,839 8/1962Great Britain. 175,483 7/ 1935 Switzerland.

ELI LIEBERMAN, Primaly Examiner.

4. AN ANTENNA WITH RADIATOR OF ADJUSTABLE EFFECTIVE LENGTH COMPRISING APLURALITY OF ELONGATED HOLLOW DIELECTRIC MAST SECTIONS ADAPTED TO NESTONE WITHIN ANOTHER IN A DEMOUNTED POSITION AND TO ENGAGE END-TO-END INAN OPERATIVE POSITION, MEANS FOR SUPPORTING SAID MAST SECTIONS IN ANUPRIGHT POSITION ENGAGED END TO END, AND A RADIATOR ELEMENT OFADJUSTABLE EFFECTIVE LENGTH SUPPORTABLE IN AN UPRIGHT POSITION BY SAIDEND TO END ENGAGED MAST SECTIONS, SAID ELEMENTS COMPRISING AN ELONGATEDFLEXIBLE CONDUCTIVE ELEMENT, ELONGATED FLEXIBLE NONCONDUCTIVE SUPPORTMEANS SECURED TO SAID CONDUCTIVE ELEMENT FOR CONTROLLABLY POSITIONINGSAID CONDUCTIVE ELEMENT LONGITUDINALLY OF SAID END-TO-END ENGAGED MASTSECTIONS MEANS INCLUDING AN IDLER PULLEY OF DRAWING IN AND FOR EXTENDINGSAID SUPPORT MEANS AND MEANS INCLUDING A SPOOL ON WHICH THE IDLER PULLEYIS MOUNTED FOR STORING THE UNEXTENDED PORTIONS OF SAID SUPPORT MEANS ANDSAID CONDUCTIVE ELEMENT.